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Response to: Partial isodicentric chromosome without mirror image?

Uploaded by Sam Rose (Journal Development Editor) on behalf of the corresponding author

The answer to Dr. Juan Ramon Gonzalez Garcia or Martin Daniel Dominguez Cruz and Juan
Ramon Gonzalez Garcia, in case there are two authors, is quite simple.

In multicolor banding (MCB) the pseudo color-band results as shown in Figure 3 of
the paper in question [1] just give an easy understandable representation of the results.
The results are deduced from the underlying fluorochrome profiles - for details on
MCB see Ref. [2]. As shown in Fig. 1 enclosed here, the MCB-fluorochrome profiles
clearly support the results as presented in [1].

In general, GTG-banding pattern is not sufficient or suited always to comprehensively
clarify a karyotype; in contrary, 70% of GTG-banding results need a correction after
MCB [3]. Thus, we used MCB, a fluorescence in situ hybridization (FISH)-banding approach
which was shown to be reliable in several hundred publications [4] also in this study
[1]. This was done also, as MCB is the only FISH-banding approach ever validated by
FISH [5] and by array-comparative genomic hybridization [6]. However, MCB needs a
lot of experienced to be interpreted correctly.

FIG-1 : Derivatives of chromosome 11 of the case presented in [1] depicted as pseudocolor-banding
results as well as as fluorchromoprofile-results.

To the editor:
Walid Al-achakar et al. [1] described a case of acute myeloid leukemia (AML-M4) with
a complex karyotype in which two der(11) chromosomes replaced both normal homologues.
After G-banding, fluorescence in situ hybridization (FISH) and array-proven multicolor
banding (aMCB) studies, they described the derivatives as der(11)(11qter->11p11.2::11p11.2->11q23::2p23->2pter)
and der(11*)(11pter->11q13::22q11.2->22q13.3::11q13->11q21::7p12->7pter). There exists
an inconsistence between the description of the former der(11) and its aMCB color
pattern. This derivative is described as a partial isodicentric chromosome (11qter->11p11.2::11p11.2->11q23::)
which should have the expected mirror image appearance depicted in the figure 1-A.
However, the observed aMCB pattern looks very different from the expected one (figure
1-B). Other inconsistence is that apparently there is no color coincidence respect
to the inserted segment (11q13->11q21) of the other der(11*) when this segment should
be duplicated in the supposed partial isodicentric chromosome (see figure 3 in reference
1).
The results of centromere-specific (not shown) and MLL FISH studies (figure 2-B in
reference 1) together with the pattern of the aMCB are rather compatible with a hypothetical
tandem arrangement, tentatively described as der(11)(11qter->11q2?1::11q?->cen->11?::11q?23.2->11q2?1::11q2?3->11q?2::2p13->2pter).
The identification of this complex chromosome is not easy since there is no normal
chromosome 11. The inclusion of a normal chromosome 11 for comparison might have made
easier the aMCB interpretation. Moreover, an image of the FISH results with the CEP-specific
probes would also be useful. Anyway, this complex arrangement would require other
specific strategies, like FISH with unique sequences, for its elucidation.

Figure Legend
Figure 1. der(11)(11qter->11p11.2::11p11.2->11q23::2p23->2pter) analysis by aMCB with
the probe-set for chromosome 11. A- Graphic expected color distribution according
to the cytogenetic description. B- der(11) chromosome image taken from the figure
3 in reference 1.